(1) Field of the Invention
The present invention relates to metal vapor control of the liquid metal fuel used in a direct contact Brayton cycle power system. More particularly the invention relates to a system for eliminating metal vapor at the working gas outlet of a closed Brayton cycle direct contact reactor/storage tank by use of an O2 afterburner.
(2) Description of the Prior Art
My invention titled Closed Cycle Brayton Propulsion System with Direct Heat Transfer, with which this application is copending, discloses the use of the more efficient Brayton cycle instead the Rankine cycle in a closed cycle underwater propulsion system. The size and weight penalty of the Brayton cycle's hot side heat exchanger is eliminated by use of direct contact heat transfer between the working fluid which is an inert gas such as helium, argon, xenon, or a mixture of inert gases, and a liquid metal bath of a material such as lithium, sodium, potassium, aluminum, magnesium, or an alloy thereof.
The closed cycle Brayton power system with direct heat transfer invention as disclosed in copending application, Navy Case No. 71843, has the problem that some of the liquid metal fuel vapor will be carried from the reactor/fuel exchanger into the working fluid stream. The volume fraction of metal vapor is relatively low; however, during a long run of the power cycle the metal accumulation can damage the regenerator, cooler, turbine, or compressor. The volume fraction of the vapor present is equal to the ratio of the partial pressure of the liquid metal to the system operating pressure, i.e. for aluminum @ 2343° F., 1 mm Hg/˜800 psi=1.6×10−6, for lithium @ 2323° F., 400 mm Hg/˜800 psi=6.5×10−4.